1. Field of the Invention
The present invention relates to a method for preparing an extract of Centella asiatica comprising a mixture of madecassoside, terminoloside and asiaticoside.
2. Brief Description of the Related Art
Centella asiatica belongs to the Umbelliferae (Apiaceae) family, particularly the Hydrocotyle subfamily. This plant has been known and used by traditional medicines for over 3000 years. It is of particular interest for the healing, sedative, analgesic, antidepressant, antidepressant and antimicrobial properties thereof.
The active compounds of Centella asiatica are pentacyclic triterpenes, which are either in the form of triterpene genins: asiatic acid (formula I) and madecassic acid (formula II), or in the form of triterpene heterosides: asiaticoside (formula III), madecassoside (formula IV) and terminoloside (formula V).

Terminoloside is a position isomer of madecassoside and has the same sugar chain, i.e. a glucose-glucose-rhamnose chain. The structure of the terpene ring of terminoloside is equivalent to that of the terpene ring of terminolic acid.
To the inventors' knowledge, no isomer of asiaticoside has been detected to date. However, it could be assumed that a position isomer of asiaticoside exists, having a similar isomerism to that existing between madecassoside and terminoloside.
The heterosides of Centella asiatica, asiaticoside and madecassoside, are sugar complexes forming the reserve forms of asiatic acid and madecassic acid, respectively, of the plant.
Triterpene molecules are of particular interest due to the collagen synthesis regulating and activating activity thereof. Genins and heterosides extracted from Centella asiatica particularly promote collagen 1 and 3 synthesis. These active substances are used in the pharmaceutical sector essentially for facilitating healing and for treating venous insufficiency. They are used in the cosmetic sector essentially as anti-wrinkle and anti-cellulite agents. The active compounds of Centella asiatica more commonly used in the prior art are asiatic and madecassic acids and asiaticoside.
Since madecassoside is very soluble in water, it is generally carried away in washing water during conventional liposoluble active substance extraction methods.
The international application WO 2004/062678 provides a method for preparing an extract of Centella asiatica comprising a mixture of madecassoside, terminoloside and asiaticoside, said method comprising a step for selective delipidation by liquid/liquid extraction followed by concentration of the hydro-alcoholic phase obtained and successive filtrations, this sequence being intended to remove asiaticoside from the mixture of madecassoside and terminoloside. However, madecassoside solubilizes a portion of the asiaticoside, this residual proportion of asiaticoside needing to be removed by silica gel chromatography, a costly purification technique which is not popular on industrial scales.